1. Field of the Invention
This invention relates to quick release tube couplings of the kind (referred to hereinafter as the kind described) having a collet with resilient arms arranged to co-operate with a cam surface on a member surrounding the collet, this cam surface being constituted by an internal surface tapering to a smaller diameter in one axial direction and engaging the arms so that the arms are forced radially inwardly by axial movement in this direction which is the direction to withdraw the tube from the coupling and wherein the collet has its arms spaced apart in the circumferential direction such that, in the absence of any tube within the collet, the arms can move radially inwardly to permit the collet to withdraw from said member by axial movement in said one direction.
2. Description of the prior art
One such coupling of the kind is described and claimed in British Patent Specification No. 1520742. This arrangement in which the collet, in the absence of the tube, can be withdrawn from the coupling enables the body member to be a unitary structure yet permits of the collet being removed and hence enables an O-ring or like sealing member inside the coupling to be replaced.
The usual practice has been to make the body members of such couplings of metal. It is an object of the present invention to provide a form of construction which enables the body member to be made out of a plastics material. The collet itself can be made out of plastics material, possibly with a stainless steel insert, as it described for example in British Patent Specification No. 1573757. A coupling formed of plastics material is particularly desirable for use for example in the handling of foodstuffs and beverages.
Heretofore it has not been possible to mould a body member for such a coupling out of plastics material with the required degree of accuracy necessary for making an effective coupling. The reason for this is that the body member essentially has a through-bore which is necessarily narrower at its two ends than is the centre part. Between the centre part of the body member and one end of the bore there must be at least one shoulder to provide a support for a resilient seal member, e.g. an O-ring into which the tube extends when put into the body member from the other end. The tube itself normally abuts against this shoulder or against another abutment. From the shoulder towards said other end, there is the cam surface which has to taper to a narrower diameter in the direction towards said other end.